netdev - Re: [PATCH v2] socket: fix struct ifreq size in compat ioctl

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Message-Id: <20180913.160155.409568197887579582.davem@davemloft.net>
Date:   Thu, 13 Sep 2018 16:01:55 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     johannes@...solutions.net
Cc:     netdev@...r.kernel.org, robert@...llahan.org,
        viro@...iv.linux.org.uk, johannes.berg@...el.com
Subject: Re: [PATCH v2] socket: fix struct ifreq size in compat ioctl

From: Johannes Berg <johannes@...solutions.net>
Date: Thu, 13 Sep 2018 14:40:55 +0200

> From: Johannes Berg <johannes.berg@...el.com>
> 
> As reported by Reobert O'Callahan, since Viro's commit to kill
> dev_ifsioc() we attempt to copy too much data in compat mode,
> which may lead to EFAULT when the 32-bit version of struct ifreq
> sits at/near the end of a page boundary, and the next page isn't
> mapped.
> 
> Fix this by passing the approprate compat/non-compat size to copy
> and using that, as before the dev_ifsioc() removal. This works
> because only the embedded "struct ifmap" has different size, and
> this is only used in SIOCGIFMAP/SIOCSIFMAP which has a different
> handler. All other parts of the union are naturally compatible.
> 
> This fixes https://bugzilla.kernel.org/show_bug.cgi?id=199469.
> 
> Fixes: bf4405737f9f ("kill dev_ifsioc()")
> Reported-by: Robert O'Callahan <robert@...llahan.org>
> Signed-off-by: Johannes Berg <johannes.berg@...el.com>

Applied and queued up for -stable, thanks Johannes.